Barrel nut assembly and method to attach a barrel to a firearm using such assembly

ABSTRACT

A firearm barrel nut assembly including a barrel nut, generally cylindrical in shape with a threaded central bore, and an externally threaded locknut which is used in conjunction with the barrel nut to secure a barrel to a firearm upper receiver. The barrel nut has an integral bushing on its exterior constructed to support either the gas tube or piston of the host firearm&#39;s operating system. The barrel nut is configured so that it may be independently and non-rotationally held within a vice or other fixture during installation of the barrel and while the locknut is tightened to a preset torque to hold the barrel in place while the barrel nut is independent of the torque applied to the locknut to properly secure the barrel to the upper receiver.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates in general, to firearms, and more particularly tobarrel nut designs which ease installation of the barrel to the frontend of the upper receiver and which offer structural features thatimprove the function of the associated gas operated firearm.

2. Description of the Related Art

Firearms in the M16 family, which include but are not limited to, theAR10, SR25, AR15, and piston driven systems and other similar designs,have been in use with military, police, and civilian shooters for nearly50 years. The M16 family of firearms includes a lower receiver having astock coupled to the rear end which is connected to an upper receiverhaving a barrel coupled to the front end. The chamber end of the barrelis received by a portion of the upper receiver and threadedly secured inplace. The threads of the upper receiver which receive the barrel nutare not timed in any way but require a minimum torque of 30 foot poundsto secure the barrel in place. The outer surface of the barrel nut has aseries of spokes, with gaps foamed between, which are used to applytorque to the barrel nut. In order to properly install the gas operatingsystem of the firearm, a gap in the spokes must be in alignment with anopening in the front of the upper receiver. This alignment is requiredbecause the gap between the spokes facilitates the entry of either apiston or a gas tube, of the gas operating system, into the interior ofthe upper receiver. To achieve this required alignment, the barrel nutis often either under- or over-torqued. Both of these conditions presenta variety of potential problems which include, but are not limited to,damage to the firearm, poor accuracy during normal operation orcompromised operational reliability.

Indirect gas operated M16 type rifles, often referred to as pistondriven, such as the design described in U.S. Pat. No. 7,461,581 (“the'581 patent”), are becoming increasingly popular within both thecommercial and military markets due to the increased operationalreliability offered by such systems. The vast majority of these newpiston driven designs rely on the prior art barrel nut common to the M16family of firearms and as such have inherited the flaws of this design.In addition to the trouble which can result from improper torque beingapplied to the barrel nut, these piston designs depend on a movingpiston, which is supported by the spokes of the barrel nut, to operate.However, the spokes of the barrel nut were not designed for this purposeand, as a result, present a weak point in the operational reliability ofthese new piston driven designs. Over time some systems which rely onthe prior art barrel nut fail because the spokes which support thepiston directly, or a removable bushing which houses the piston, startto bend or break, rendering the firearm inoperable. Therefore a needexists for a barrel nut design that will remedy the foregoing and otherdeficiencies inherent in the prior art.

SUMMARY OF THE INVENTION

Accordingly several objects and advantages of the present invention are:

-   -   (a) To overcome the disadvantages associated with the        conventional barrel nut which can be under- or over-torqued in        order to better accommodate the gas operating system;    -   (b) To provide a barrel nut assembly with an integral bushing to        support a piston or to guide the gas tube of a gas operated        firearm; and    -   (c) To provide a barrel nut which is oriented about the barrel        and receiver independently of the torque which is applied to        secure the barrel in place.

In accordance with one embodiment of the present invention, a barrel nutassembly including a barrel nut and a locknut for coupling a barrel tothe receiver of a firearm are provided. The barrel nut has internalthreads and an external flange which is designed to be held in a fixturethat is secured in a vice during barrel installation. The barrel nutbody is designed to receive the threaded extension of the upper receiverin its back side and the chamber end of the barrel in its front side. Anannular locknut, which has a central opening to receive the barrel, isused to secure the barrel to the host firearm's receiver. A presettorque value is applied to secure the locknut, and thereby the barrel,into place. While the locknut is being rotated, the barrel nut and upperreceiver are held securely in a fixture which prevents the unintentionalrotation and resulting misalignment of the barrel nut in relationship tothe upper receiver. Further, the locknut places torque directly againsta portion of the barrel, effectively compressing it against the frontpart of the upper receiver. The barrel nut assembly design and method ofinstallation according to the present invention eliminate the problemsinherent in the prior art as a result of applying an inappropriatetorque value to a barrel nut in an effort to align the barrel nut withthe gas tube of the firearm's operating system during barrelinstallation.

The body of the barrel nut also includes an integral bushing which isdesigned to receive and support a portion of a gas piston or gas tube ofthe firearm's operating system. Having a bore designed to be alignedwith an opening present on the forward face of the upper receiverthrough which the operating rod passes, the integral bushing isstructurally sound and will not bend or deform even after prolonged useof the host firearm. Accordingly the present invention provides a barrelnut assembly that affords the user with a method and apparatus foraligning the bushing bore with the upper receiver opening that isindependent of the torque required to properly secure the barrel to theupper receiver.

Still further objects and advantages will become apparent from aconsideration of the ensuing description and drawings where likereference numerals refer to corresponding elements throughout.

DESCRIPTION OF THE DRAWINGS

The characteristic features of the invention, together with furtheradvantages thereof, will be better understood from the followingdescription considered in connection with the accompanying drawings inwhich a preferred embodiment of the present invention is illustrated byway of example. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended to define the limits of the invention.

FIG. 1 is an exploded perspective view of an upper receiver with abarrel being secured with a barrel nut assembly in accordance with thepresent invention.

FIG. 2 is an illustration of a barrel nut assembly in accordance withthe present invention.

FIG. 3 is a front end perspective view of the barrel nut of the barrelnut assembly shown in FIG. 2.

FIG. 3A is a front end view of the barrel nut shown in FIG. 1.

FIG. 4 is a front end perspective view of the locknut of the barrel nutassembly shown in FIG. 2.

FIG. 5 is a detailed side cutaway view showing the barrel nut assemblyaccording to the present invention in use.

FIG. 6 is a perspective view of a specialized wrench used to secure thelocknut against the annular flange on the barrel when securing thebarrel to the upper receiver, as shown in FIG. 1, using the barrel nutassembly as shown in FIG. 2.

FIGS. 7A and 7B show side perspective views of a rifle equipped with thebarrel nut of the present invention secured in a fixture, duringinstallation of the lock nut, the fixture shown in the opened positionin FIG. 7A and in the closed position in FIG. 7B.

FIG. 8 is a perspective view of a prior art barrel nut.

FIG. 9 is an exploded view of an upper receiver which uses a prior artbarrel nut to secure the barrel to the receiver.

FIG. 10 is a side view of an upper receiver group using the barrel nutassembly of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is directed to a barrel nut assembly for use withthe AR-10, AR-15, SR25, M16 variety and other derivatives to includethose which use a gas piston in place of a conventional gas tube. Unlessotherwise specified, the various components which make up the triggermechanism, upper receiver assembly, lower receiver assembly, buttstockassembly, bolt assembly and barrel assembly are those found on the priorart M16 and M4 rifles and their various embodiments.

As used herein, the word “front” or “forward” corresponds to the endnearest the barrel (i.e., to the right as shown in FIG. 1); and “rear”or “rearward” or “back” corresponds to the direction opposite the end ofthe barrel, where the receiver is located (i.e., to the left as shown inFIG. 1).

The present invention is directed to a barrel nut assembly for securinga barrel to the front end of a receiver. In FIG. 1 there is illustratedan exploded perspective view of a firearm upper receiver group. Shown isthe receiver 20 which has an opening 22 on its forward face and athreaded extension 21. The threaded extension 21 is configured tothreadedly receive the rearward end of the barrel nut 12. The barrel 30for the host firearm is shown with a flash hider 34 and gas block 32installed at its forward end. The construction of the barrel 30 is of aconventional M16 type. The rearward or chamber end 23 of the barrel 30has an annular flange 31.

The piston assembly, generally designated by reference numeral 33,incorporates a piston cup 35 at its forward end, an operating rod 37 atthe back end and a connecting rod 29 located therebetween. The gas block32 incorporates a gas nozzle 36 which is received by the piston cup 35.The piston assembly 33 and the gas nozzle 36 are components of theoperating system being used with the preferred embodiment. The specificcomponents and features which make up the piston assembly 33 and the gasnozzle 32, along with the methods of their installation, are describedin the '581 patent and co-pending, commonly owned, patent applicationU.S. Ser. No. 12/801,001, which are expressly incorporated by referenceas if fully set forth herein. Any manner in which the piston assembly 33and the gas nozzle 36 differ from '581 patent will be disclosed herein.

As shown in isolation in FIG. 2, the barrel nut assembly, generallydesignated by reference number 10, includes the barrel nut 12, and alocknut generally designated by reference numeral 11. The barrel nut 12has a threaded longitudinal bore 15 that extends from a front end 100 ofthe barrel nut to the rear end 102 thereof. As shown in FIG. 1, thefront end 100 of the barrel nut 12 receives the rear or chamber end of abarrel 30, while the rear end 102 of the barrel nut is threadedlysecured to the front extension 21 of the receiver 20.

The barrel nut 12, shown best in FIG. 3, also incorporates an integralbushing 16 mounted longitudinally along the top surface of its exterior.The bushing 16 has a through bore 18 that is generally parallel with thelongitudinal bore 15 and defines an inner wall 106 through which theoperating rod 37 of the firearm passes during normal operation of thehost firearm. The bushing 16 provides a robust support structure for theoperating rod 37 and other components of the gas operating system of thehost firearm.

The forward end 100 of the barrel nut includes an exterior flange 13,best shown in FIG. 3A, having at least two and preferably three squaredoff sections 104 spaced 90° apart to render the forward face of thebarrel nut essentially square. These squared off sections 104 areconfigured to be received within and captured by a fixture (see FIGS. 7Aand 7B) used to lock the receiver and barrel nut in place to preventrotation thereof when mounting the barrel, as will be describedhereinafter.

The opening edge 14 about at least the bottom portion 114 of theentrance into the through bore 18 of the bushing 16 is chamfered. In theillustrated embodiment, the opening edge is chamfered all the wayaround, with the chamfered bottom portion 114 of the edge 14 of thethrough bore 18 being more substantial than the chamfer extending aboutthe top portion 115 of the through bore 18. This opening edge 14 isconfigured to receive and support the chamfered rear end 39 of springcup 38 during and upon installation of the piston assembly 33 shown inFIG. 5. The chamfering of the edge 14 provides “wiggle room” which aidsin the installation of the piston assembly. It should also be understoodthat the opening edge 14 about the face of the through bore 18 cansupport or be modified to support, spring cup equivalents or the springsof other piston-operated firearms. In general, the opening edge 14 ofthe through bore 18 of the barrel nut bushing 16 is designed to providea robust structure to support the spring cup 38 or return spring of apiston driven firearm and provide a surface for it to press againstduring operation.

FIG. 4 shows an isolated front end perspective view of the locknut 11 ofthe barrel nut assembly. The locknut has threads 117 about its exteriorthat are configured to enable the locknut 11 to be threadedly receivedinto the threaded bore 15 of the barrel nut 12 during assembly. Thelocknut includes a grippable structure preferably embodied as aplurality of cutouts or grooves 17 spaced evenly about the forward face119 of the locknut 11. These grooves 17 are configured to engage with acomplementary gripping structure on a wrench 40 (shown in FIG. 6) whichis used to apply torque to the locknut 11 during assembly. The locknut11 secures the barrel 30 to the barrel nut 12 and to the upper receiver.Because torque is applied to the locknut while the barrel nut is heldstationary in the fixture, the barrel nut assembly in accordance withthe present invention allows for consistent torque to be used whensecuring the barrel 30 in place.

FIG. 5 shows a side cutaway view of upper receiver 20 with barrel 30being retained by the barrel nut 12 and lock nut 11 of the barrel nutassembly 10 according to the present invention. After threading thebarrel nut 12 onto the threaded extension 21 of the receiver 20, therearward end of the barrel 30 is inserted into the threaded bore 15 ofthe barrel nut 12. When mounted, the back side of the annular flange 31of the barrel 30 is aligned with and seated against the forward face 108of the receiver's threaded extension 21. The locknut 11 is threaded intothe threaded bore 15 of the barrel nut and comes to rest against thefront side of annular flange 31 when tightened, thereby retaining thebarrel 30 in place.

A specially designed wrench, generally designated by reference numeral40, is used to secure the lock nut 11 to the barrel nut 12 as shown inFIG. 6. The wrench 40 has a body 138 with a crescent shaped head,generally designated by reference numeral 142, defining a C-shapedopening 144 with an inner periphery 146 about one end. The innerperiphery includes a gripping structure embodied as a plurality of teeth43 which project outwardly from the forward edge 139 of the innerperiphery. The teeth 43 are generally perpendicular to the face 140 ofone side of the wrench and are configured to engage with the grooves 17on the front face of the lock nut 11 (see FIGS. 4 and 7A). The body 138has an aperture 44 therein which is configured to receive the ½″ drivemember of any conventional socket or torque wrench. It is to beexpressly understood that the aperture 44 which receives the drivemember of the wrench could be constructed to receive any size or type ofdrive mechanism found on a wrench.

FIGS. 7A and 7B show a fixture 80 which, in a preferred embodiment, hastwo halves 110 and 112 interconnected by pivot rod 114. FIG. 7A showsthe fixture in its open position to receive the upper receiver 20 of thefirearm with a barrel nut 12 threaded into place. The interior of thefixture 80 is configured to receive and rotationally restrain the upperreceiver 20 and the forward face 79 has a cutout 82 to rotationallyrestrain the barrel nut 12.

In particular, the fixture 80, which is shown in the opened position inFIG. 7A, has a cutout 82 about its forward face 79. The cutout 82 hastwo opposed sides and a bottom which form three sides of a square. Thetop or fourth side is recessed in order to accommodate the bushing 16.When the receiver and the barrel nut are positioned in the fixture, thethree squared off sections 104 of the flange 13 are aligned with thethree sides of the cutout 82. Therefore, when the halves 110, 112 arejoined to place the fixture 80 in the closed position as shown in FIG.7B, the cutout 82 effectively captures the squared off sections of theflange 13 on the forward face of the barrel nut 12 and preventsrotational movement of the barrel nut while the lock nut is beingtightened within the barrel nut's longitudinal bore 15. The portion ofthe fixture 80 located below the stops 81 (as shown in FIG. 7B) isconfigured to be grasped by a vice (not shown) or similar apparatuswhich is used to hold the fixture 80 in place when the fixture is beingused to restrain the upper receiver 20.

A prior art barrel nut 50 is shown in FIG. 8. The prior art barrel nut50 is configured to have a series of spokes 51 which define troughs 52and an inner circumvolving edge 53 which holds the barrel 54, inconnection with the barrel nut 50, in place on the upper receiver 55,shown in FIG. 9.

FIG. 9 illustrates an exploded view of a complete upper receiverassembly for an M16 type rifle using the prior art barrel nut 50 tosecure the barrel 54 to the receiver 55. The rearward end of the barrel54 is received by the threaded extension 56 of the receiver 55. Thebarrel nut 50 has a through bore which is configured to threadedlysecure to the threads present on the threaded extension 56 of thereceiver 55. The circumvolving edge 52 present within the interior ofthe barrel nut 50 secures the barrel 54 to the receiver 55 by placingforce against the annular flange 57 of the barrel 54 and pushing itagainst the forward face of the threaded extension 56 of the receiver55. There are a series of spokes 51 and troughs 52 present about theexterior of the barrel nut 50. When torque is being applied to thebarrel nut 50 to secure the barrel 54 in place, the final positioning ofthe barrel nut has to place a trough 52 in alignment with an opening 58present on the forward face of the receiver 55. When aligned with theopening 58 on the receiver, this trough allows the gas tube 60, orpiston in some cases, to extend from the gas block 59 through the trough52 and the opening 58 into the interior of the receiver 55 where the gastube or piston is placed into communication with the bolt carrier, notshown but well known in the prior art.

If a spoke 51 of the prior art barrel nut is in line with the opening 58on the receiver 55 when the barrel nut is torqued, the gas tube 60cannot be properly installed, rendering the rifle inoperable. There isno effort to time the threads of the threaded extension 56 and thebarrel nut 50 during the manufacturing process. As a result, duringinstallation the barrel nut is often torqued into place multiple timesin an attempt to properly align a trough 52 of the barrel nut with theopening 58 in the receiver 55. This can result in a situation where thealignment of a trough 52 with the opening in the receiver 55 will onlyoccur by either over-torquing the barrel nut 50, under-torquing thebarrel nut 50, or removing the barrel nut 50 entirely and starting overwith a new barrel nut, which may have the same or a similar problem. Incases where the barrel nut 50 is over-torqued, the spokes 51, which areused in conjunction with a tool to apply torque to the barrel, canbecome brittle and break. This is a condition of particular concern whena piston is used in place of the gas tube 60, which is often supportedon the spokes 51. Over-torquing the barrel nut 50 and thereby the barrel54 can also negatively affect the accuracy of the host firearm.

To secure a barrel 30 to an upper receiver 20 of an M16 type firearmusing the barrel nut assembly 10 in accordance with the presentinvention, the barrel nut 12 is threaded onto the threaded extension 21of the upper receiver 20 until the barrel nut stops. The barrel nut isthen reverse threaded until the through bore 18 of the bushing 16 isaligned with the opening 22 on the face of the receiver 20. Theresulting subassembly of the upper receiver and the barrel nut is thenplaced within a fixture 80 which is secured within a vice to prevent anyrotational movement of the barrel nut 12 and upper receiver 20. A barrel30 of desired length is then selected, with the chamber end 23 thereofbeing inserted into the barrel nut 12 until the annular flange 31 of thebarrel 30 is aligned with and comes to rest against the forward face 108of the threaded extension 21 (see FIGS. 1 and 5). At the same time, theannular flange 31 is also contained within the interior of the barrelnut 12. The locknut 11 slides into and down the barrel and is thenthreadedly secured within the threaded bore 15 of the barrel nut 12. Thelocknut 11 is secured in place with the appropriate torque value usingthe wrench 40. The opening 144 of the wrench 40 is of sufficient size tofit about the barrel 30, and the teeth 43 around the periphery of theopening are constructed to interface with the grooves 17 on the forwardface of the locknut 11. A secondary wrench with a drive is then used toapply a predetermined torque value to the locknut 11, thus securing thelocknut 11 and thereby the barrel 30 into place. The gas block 32 andflash hider 34 are then installed onto the barrel 30, the manner ofwhich is well known in the prior art.

The piston assembly 33 is assembled in essentially the same manner asdescribed in the '581 patent. Initially, the piston cup 35 isindependently placed on the gas nozzle 36. The rear end of the operatingrod 37 is then inserted into the through bore 18 of the bushing 16 andinto the opening 22 of the receiver 20 by grasping the forward end ofthe operating rod 37 and thereby compressing the spring of the pistonassembly 33. With the spring compressed, the operating rod 37 may berotated into a position which places it in line with the rearward faceof the piston cup 35. While holding the operating rod 37 in itscompressed position, the connecting rod 29 is then inserted into theopening (not shown) present on the forward end of the operating rod 37.This assembly is then aligned with the opening (not shown) present onthe back side of the piston cup 35 and released so that a forwardportion of the connecting rod 29 is received by the opening on the backside of the piston cup 35, thereby holding the operating rod 37,connecting rod 29, and piston cup 35 in operational alignment. Thechamfered edge 14 present at the opening of the through bore 18facilitates the initial insertion or removal of the operating rod 37.Thus the installation of the new barrel nut assembly 10 has beendescribed. By reversing the steps outlined above the barrel nut assembly10 may be removed.

FIG. 10 shows a complete upper receiver and barrel assembly 70consisting of an upper receiver 20 with a barrel 30 that has beensecured in place through the use of the barrel nut assembly 10 describedherein. A handguard 41, being secured to the barrel nut 12 through theuse of a clamp 42, has been installed to protect the user's hand fromdirect contact with the barrel 30 while the firearm is being operated.This handguard is fully disclosed in copending application Ser. No.12/217,874, commonly owned by the assignee of the instant application.The clamp 42 used herein to secure the handguard to the barrel nut 12has been configured to accommodate the bushing 16 present on the barrelnut 12 described herein.

It should also be noted that the piston assembly 33, gas nozzle 36 andgas block 32 may easily be replaced with the gas block 59, gas tube 60and other components of prior art gas operating systems withoutdeparting from the purpose and advantage of the barrel nut assembly 10of the present invention as described herein.

CONCLUSION, RAMIFICATIONS, AND SCOPE

Accordingly, the barrel nut assembly according to the present inventionprovides an apparatus and method for securing a barrel to the receiverof a firearm. The barrel nut has an integral bushing 16 with a throughbore 18 that is aligned with the opening 22 in the receiver so that theoperating rod 37 of the piston assembly 33 may pass unhindered into theinterior of the receiver. By supporting the operating rod of the pistonassembly, the integral bushing provides a more robust means ofsupporting the operating rod and is not prone to structural failure asare the spokes of a conventional barrel nut, the disadvantages of whichhave been described above.

In addition, the provided method of orienting the through bore 18 of thebushing 16 with the opening 22 of the receiver is independent of thetorque applied to the locknut used to secure the barrel to the receiver,offering the significant advantage of being able to use a consistent,preset torque value to secure the barrel to the receiver. This use of aconsistent, preset torque value is an advantage as compared to prior artmethods of securing a barrel to a receiver through the use of aconventional barrel nut.

While there is shown and described the present preferred embodiment ofthe invention, it is to be distinctly understood that this invention isnot limited thereto but may be variously embodied without departing fromthe intended scope of the present invention. From the foregoingdescription, it will be apparent that various changes may be madewithout departing from the spirit and scope of the invention as definedby the following claims.

What is claimed is:
 1. A barrel nut assembly for connecting a firearmbarrel to the receiver of a gas operated rifle, said barrel nut assemblycomprising: a barrel nut which is generally cylindrical in shape anddefines a generally longitudinally extending bore extending from a backend of said nut along a longitudinal axis to a front end of the nut,said bore having internal threads to be secured at the rear end to anexternally threaded front end part of the receiver, the front end ofsaid bore being configured to receive a rear end portion of the firearmbarrel therein; and a locknut having external threads that engage withthe internal threads in the barrel nut bore, enabling the locknut to bethreadedly received within and connected to the barrel nut, said locknutbeing configured to compressively engage and secure said firearm barrelin position against said receiver as the locknut is screwed into thebarrel nut and tightened to a preset torque value, a rotationalorientation of said barrel nut about the barrel being independent oftorque applied to the locknut.
 2. The barrel nut assembly of claim 1,wherein a forward face of said barrel nut has an external structureconfigured to be captured within a fixture used to secure the receiverand prevent rotation of said barrel nut when said locknut is beingsecured within said longitudinal bore.
 3. The barrel nut assembly ofclaim 2, wherein the external structure is a flange.
 4. The barrel nutassembly of claim 3, wherein the flange makes the forward face of thebarrel nut substantially square.
 5. The barrel nut assembly of claim 1,wherein said barrel nut includes an integral support structure for atleast a portion of the host firearm's gas operating system.
 6. Thebarrel nut assembly of claim 5, wherein said support structure includesa longitudinally extending bore configured to receive a portion of thegas operating system.
 7. The barrel nut assembly of claim 5, whereinsaid integral structure includes a bushing positioned on a top side ofsaid barrel nut having a longitudinally extending bore configured toreceive a gas tube of the host gas operating firearm's direct gasoperating system.
 8. The barrel nut assembly of claim 1, wherein aforward face of said locknut includes a grippable structure configuredto be engaged with a complementary gripping structure on a tool that isused to apply torque to said locknut.
 9. The barrel nut assembly ofclaim 1, wherein a forward face of said locknut is provided with aplurality of spaced grooves configured to engage with correspondinglyspaced teeth on a wrench which is used to apply torque to said locknut.10. A method of securing a barrel having an annular flange proximate toa rear end of said barrel, to a firearm using a barrel nut, a locknutand a fixture which is configured to receive a receiver of the firearmand the barrel nut and restrain both from rotational movement, thereceiver having an externally threaded front end part which isconfigured to be threadedly engaged within a rear end of the barrel nut,the barrel nut having an internally threaded central bore that receivesa chamber end of the barrel and a bushing with a bore therethrough whichaligns with an opening located on the front face of the firearmreceiver, the bore in the bushing and the opening in the firearm beingconfigured to receive a part of the firearm's operating system therein,the lock nut being configured to slide onto and down the barrel andhaving external threads to threadedly engage with internal threads on afront end of the barrel nut bore, the method comprising the steps of:threadedly securing the barrel nut about the externally threaded frontend part of the receiver, the barrel nut being rotated at least onecomplete revolution, until the bore in the bushing aligns with theopening in the front face of the receiver; securing the fixture about atleast the receiver of the firearm and a portion of the barrel nut, saidbarrel nut having an external structure configured to engage with saidfixture and prevent rotation of said barrel nut while torque is beingapplied to the locknut to secure the barrel to the receiver; insertingthe chamber end of the barrel into the barrel nut until the barrel seatsinto place against an abutting face on the firearm receiver and theannular flange is contained within the central bore of the barrel nut;sliding the locknut down the barrel toward the chamber end andthreadedly securing the locknut to the barrel nut by rotating thelocknut until the locknut comes to rest against the annular flange onthe barrel; and tightening said locknut against said annular flange to apreset torque value.
 11. The method of claim 10, further comprising thestep of using a vice to secure the fixture in place and preventunintentional movement thereof.
 12. The method of claim 10, furthercomprising the step of using a wrench with a crescent shaped head havinga plurality of teeth projecting from an inner periphery configured toengage with grooves formed on the forward face of the locknut, thewrench being used to rotate and secure the locknut against the annularflange of the barrel.
 13. A gas operated firearm comprising: an upperreceiver having a forward end with an externally threaded extension andan opening for receiving an operating rod of a gas operating system; abarrel having an annular flange proximate a rear end of said barrel; agas operating system having said operating rod; and a barrel nutassembly for connecting said barrel to said upper receiver, said barrelnut assembly including: an internally threaded barrel nut threadinglysecured to said externally threaded extension of the receiver and beingconfigured to receive a rear end portion of the firearm barrel therein,said barrel nut having a through bore adjacent its periphery that isaligned with said receiver opening to receive said operating rodtherethrough; and a locknut having external threads that engage with theinternally threaded barrel nut to compressively engage and secure saidfirearm barrel in position against said receiver, a back side of saidbarrel annular flange being seated against a forward face of thethreaded extension of the receiver.
 14. The gas operated firearm ofclaim 13, wherein a forward end of said barrel nut includes an exteriorflange having at least two squared off sections to render a forward faceof said barrel nut substantially square, said squared off sections beingconfigured to be received within and captured by a fixture used to lockthe receiver and barrel nut in place to prevent rotation thereof whenmounting the barrel.
 15. The gas operated firearm of claim 13, wherein aforward face of said locknut includes a grippable structure configuredto be engaged with a complementary gripping structure on a tool that isused to apply torque to said locknut when compressively engaging andsecuring said firearm barrel in position against said receiver.
 16. Thegas operated firearm of claim 13, wherein a forward face of said locknutis provided with a plurality of spaced grooves configured to engage withcorrespondingly spaced teeth on a wrench which is used to apply torqueto said locknut when compressively engaging and securing said firearmbarrel in position against said receiver.
 17. A barrel nut assemblyapparatus comprising: a barrel nut assembly for connecting said barrelto said upper receiver, said barrel nut assembly including: a barrel nutwhich is generally cylindrical in shape and defines a generallylongitudinally extending bore extending from a back end of said nutalong a longitudinal axis to a front end of the nut, said bore havinginternal threads to be secured at the rear end to an externally threadedfront end of the receiver, the front end of said bore being configuredto receive a rear end portion of the firearm barrel therein; and alocknut having external threads that engage with the internal threads onthe barrel nut bore, enabling the locknut to be received within andconnected to the barrel nut, said locknut being configured tocompressively engage and secure said firearm barrel in position againstsaid receiver as the locknut is screwed into the barrel nut and securedto a preset torque value, a rotational orientation of said barrel nutabout the barrel being independent of torque applied to the locknut; awrench with a crescent shaped head having a plurality of teethprojecting from an inner periphery configured to engage with groovesformed on the forward face of the locknut, the wrench being used torotate and secure the locknut against the annular flange of the barrel;and a fixture configured to receive a receiver of the firearm and thebarrel nut and restrain both from rotational movement while said locknutis being torqued.